As this release has adopted ES2015, it now uses Map and Set native collections. It also adds the ability to accept iterables. It introduces new functions d3.group and d3.rollup. New helpers have been added to d3-array, including d3.greatest, d3.quickselect, and d3.fsum. D3 now passes events directly to listeners, replacing the d3.event. It has introduced d3-delaunay, replacing d3-voronoi, to enhance performance, robustness, and search. It has introduced d3-geo-voronoi, a module that uses e3-dlaunay for geographical data. These changes make it possible to handle both Voronoi and Delaunay diagrams.
This release adds minor feature improvements to many of the modules, which includes some backward-compatible changes, like dropping support for Bower.
D3.js 6.0 is available for download from the project website. It requires a browser that supports ES2015. As a side note, the project has released v6.1 on August 31.